The conventional sandglass timer comprises two closed chambers that are interconnected by a narrow neck, and sand or other particulate material is located within the timer in such a way that it may flow from one chamber to the other, under the influence of gravity, by way of the neck. The timer is usually formed from glass or a transparent plastics material and a predetermined period of time is deemed to have passed when the entire quantity of sand is seen to pass from one chamber to the other.
A problem with the conventional sandglass timer is that the entire quantity of sand must pass from one chamber to the other before the timer can be inverted to commence a new timing operation, and this can be rather irritating under some conditions. For example, if the timer is being used to time-out the period allowed for a move in a board game and one participating player completes the move well before the sand transfer from one chamber to the other has been completed, then the players must wait patiently until the operation has been concluded before play may recommence.